refactor(M03): extract M2 runtime mesh finalizer

Work-Package: M03-RND-M2-RUNTIME-MESH-FINALIZER-001
Agent: sindo-main-codex
Tests: 37 headless renderer/coordinate contracts pass; checkpoint dry-run 7/7; documentation and coordination gates pass
Fidelity: preserves refresh version 2, classifier, rebuild and fallback transitions; no visual parity claim

RENDER.md

@@ -39,6 +39,7 @@ Paired run 2026-07-11 подтвердил крупный coordinate/placement g
 - `src/render/m2/m2_mesh_load_pipeline_state.gd` - static M2 threaded-load request records, terminal statuses and completion-order finalize FIFO without I/O or Mesh ownership.
 - `src/render/m2/m2_mesh_resource_cache_state.gd` - normalized-path prepared static M2 Mesh references with final-shutdown lifetime.
 - `src/render/m2/m2_mesh_resource_extractor.gd` - first-Mesh selection from direct/PackedScene/Node inputs with temporary instance cleanup.
+- `src/render/m2/m2_runtime_mesh_finalizer.gd` - refresh version, classifier lifetime, M2Builder rebuild and original-Mesh fallback.
 - `src/scenes/streaming/eastern_kingdoms_streaming.tscn` - текущая сцена для проверки Azeroth/Eastern Kingdoms.
 - `addons/mpq_extractor/loaders/adt_builder.gd` - сборка ADT terrain, control splat материалов и MH2O liquids.
 - `addons/mpq_extractor/loaders/m2_builder.gd` - сборка статического M2 mesh/material.
@@ -807,7 +808,12 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - Billboard metadata is resolved per drawn vertex through the skin section bone palette and vertex bone indices. This avoids treating an entire mixed surface as billboard just because the palette contains a billboard bone.
 - `M2Builder` stores billboard pivot/mode in `Mesh.ARRAY_CUSTOM0` as RGBA float data. `CUSTOM0.xyz` is the Godot-space bone pivot; `CUSTOM0.w` is the billboard mode: spherical, lock X, lock Y, or lock Z.
 - `WowM2Material` applies camera-facing billboarding in the vertex shader for marked vertices. This works with grouped ADT M2 `MultiMesh` batches because the shader uses each instance transform.
-- Runtime M2 cache refresh now has `M2_MATERIAL_REFRESH_VERSION`. Old cached `.tscn/.glb` meshes are replaced in memory from raw `.m2` only when the raw model actually needs custom billboard attributes or UV-rotation data. Do not rebuild every stale cached M2 during streaming: creating fresh materials for ordinary props can exhaust the D3D12 resource descriptor heap.
+- Runtime M2 cache refresh uses material refresh version `2` (now
+  `M2RuntimeMeshFinalizer.MATERIAL_REFRESH_VERSION`). Old cached `.tscn/.glb`
+  meshes are replaced in memory from raw `.m2` only when the raw model actually
+  needs custom billboard attributes or UV-rotation data. Do not rebuild every
+  stale cached M2 during streaming: creating fresh materials for ordinary props
+  can exhaust the D3D12 resource descriptor heap.
 - Verified with `ElwynnGrass1.m2`: native data exposes a billboard batch, the built mesh contains `CUSTOM0`, and the M2 shader compiles with the billboard uniform enabled.
 - Remaining parity work: many Elwynn tree canopy M2s do not carry billboard bone flags, so their flat-looking leaves are a separate material/geometry parity issue, not this bone-billboard path.
 
@@ -817,7 +823,8 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - Texture transform dictionaries now expose static UV rotation matrices and approximate Z-rotation speeds, in addition to existing translation, translation speed and scale.
 - `WowM2Material` applies UV rotation and scale around WoW's texture center `(0.5, 0.5)`, then applies translation/scroll. This is closer to the client path shown by `CM2Model::AnimateTextureTransformsMT`.
 - All four M2 texture stages receive UV rotation and rotation-speed uniforms, matching the existing four-stage texture binding path.
-- `M2_MATERIAL_REFRESH_VERSION` and `M2Builder.MATERIAL_FORMAT_VERSION` are bumped to `2`, so cached M2 meshes are rebuilt in memory when raw `.m2` data is available.
+- Runtime M2 material refresh and `M2Builder.MATERIAL_FORMAT_VERSION` are `2`,
+  so stale cached M2 meshes can be rebuilt in memory when raw `.m2` data is available.
 - Verified with `Spells/ArcaneForceShield_Blue.m2`: native data exposes a non-identity UV rotation, the built material receives the stage rotation uniform, and the shader compiles.
 
 ## 2026-07-08 Renderer Material Regression Smoke
@@ -1053,9 +1060,9 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - Invalid batch variants and combo/transform indices remain skipped. The first
   decision for a normalized path remains cached until the same two historical
   map/shutdown clear sites.
-- `StreamingWorldLoader` still loads raw M2 data, checks
-  `M2_MATERIAL_REFRESH_VERSION`, calls `M2Builder`, adopts/falls back to Meshes
-  and owns ResourceLoader/finalization budgets.
+- `StreamingWorldLoader` still loads raw M2 data and owns ResourceLoader,
+  returned-Mesh adoption and finalization budgets. Refresh-version checks,
+  M2Builder rebuild and fallback now belong to `M2RuntimeMeshFinalizer`.
 - No cache version, shader, material, geometry or visible rule changed. Synthetic
   predicate timing is not asset-backed descriptor-pressure/p95/p99 evidence.
 
@@ -1100,6 +1107,19 @@ $exe = Join-Path $env:TEMP 'godot-4.6.1-openwc\Godot_v4.6.1-stable_win64.exe'
 - Cache formats, traversal rules, profiles and visible output are unchanged.
   Synthetic traversal timing is not asset-backed leak or p95/p99 evidence.
 
+## 2026-07-17 M2 Runtime Mesh Finalizer
+
+- `M2RuntimeMeshFinalizer` now owns material refresh version `2`, stale-Mesh
+  rebuild classification, M2Builder rebuild and original-Mesh fallback.
+- Current Meshes still skip raw `.m2` loading. The loader retains FileAccess/
+  ClassDB M2Loader I/O and supplies raw data only when the finalizer reports a
+  stale Mesh; both historical decision-cache clear sites are preserved.
+- Billboard/UV-rotation predicates, rebuild extraction, metadata key and failure
+  fallback are unchanged. Cache adoption, missing state, permits and MultiMesh
+  materialization remain loader-owned.
+- Synthetic triangle rebuild/fallback timing is not asset-backed material,
+  descriptor-pressure/leak or p95/p99 evidence.
+
 ## 2026-07-17 WMO Placement Resolver Extraction
 
 - `WmoPlacementResolver` now owns lowercase/slash cache-key normalization,